Present modes of drug delivery such as topical application, oral delivery, and intramuscular, intravenous and subcutaneous injection may result in high and low blood concentrations and/or shortened half-life in the blood. In some cases, achieving therapeutic efficacy with these standard administrations requires large doses of medications that may result in toxic side effects. The technologies relating to controlled drug release have been attempted in an effort to circumvent some of the pitfalls of conventional therapy. Their aims are to deliver medications on a continuous and sustained manner. Additionally, local control drug release applications are site or organ specific.
In response to these issues, reservoir delivery systems have been explored. Non-biodegradable drug delivery systems include, for example, Vitrasert® (Bausch & Lomb), a surgical implant that delivers ganciclovir intraocularly; Duros® (Durect Corp.), surgically implanted osmotic pump that delivers leuprolide actetate to treat advanced prostate cancer; and Implanon® (Organon International), a type of subdermal contraceptive implant.
Biodegradable implants include, for example, Lupron Depot (TAP Pharmaceutical Prods., Inc.), a sustained-release microcapsule injection of luteinizing hormone-releasing hormone (LH-RH) analog for the treatment of prostate cancer; the Surodex® dexamethasone anterior segment drug delivery system (Oculex Pharmaceuticals, Inc.), and Nutropin Depto® (Genentech), micronized particles of recombinant human growth hormone embedded in polylactide-coglycolide (PLG) microspheres.
Additionally, polyethylene glycol conjugations (pegylation) to reduce the frequency of administration are now in use. One example, pending FDA licensure, is Macugen™ (Eyetech Pharmaceuticals, Inc.), a pegylated anti-VEGF aptamer, for use in treating wet macular degeneration.
There remains a need for a more economical, practical, and efficient way of producing and manufacturing drug delivery systems that could be used locally or systemically, in solid, semi-solid, or liquid formulations.